| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
| Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, ITAGAKI Takahiro <itagaki(dot)takahiro(at)lab(dot)ntt(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Remove xmin and cmin from frozen tuples |
| Date: | 2005-09-06 23:02:20 |
| Message-ID: | 21437.1126047740@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
"Jim C. Nasby" <jnasby(at)pervasive(dot)com> writes:
> If the 4 header fields in question were just normalized out, wouldn't
> all the semantics continue to work the same? All I'm envisioning is
> replacing them in each tuple with a pointer (vis_id) to another
> datastore that would be roughly equivalent to:
> CREATE TABLE visibility (
> vis_id SERIAL,
> xmin int,
> xmax int,
> cmin int,
> cmax_xmax int
> )
> Of course you wouldn't use an actual table to do this, but hopefully
> this clarifies my idea.
Let's see ... replace every tuple access with TWO tuple accesses
... yes, that should improve performance nicely. And no, I'm not
sure the semantics are the same, particularly w.r.t. atomicity of
state changes.
regards, tom lane
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